Comparative Corrosion Tests on Steel Plates Rolled From Continuously Cast Slabs and Rolled From Mold Cast Ingots

From each of four different heats of ship steel (C 0.15%, Mn 0.9 to 1.3%) one portion has been cast continuously to slabs, another to ingots in stationary molds. Hot rolled 1 5 mm plates from each of these 8 variants were compared as to their corrosion resistance in a number of test programs including immersion in sea water, brackish water, and fresh water up to 51 months; exposure to marine atmosphere up to 39 months; and accelerated tests in a salt spray chamber and in a flowing sea water simulator. Differences in attack figures between the two types of materials were small and probably due to experimental scatter. It is, therefore, concluded that for all practical purposes, the two casting methods can be considered as equivalent with respect to the corrosion resistance of the rolled steel plate. Samples from all eight steel variants have also been subjected to microcorrosion testing according to Norén-Brandel. Significant differences in "active" sulfide frequences between the two groups were found. Still more obvious differences, however, appeared between different heats, irrespective of casting method. As stated above, no corresponding differences in corrosion behavior have been found, and the microcorrosion test method therefore must be regarded as lacking prognostic value for corrosion resistance of ship plate.